Generally, ornithopters have structures such that rotating shafts of drive motors are coupled to main wings through connecting rods and gear trains. In such an ornithopter, the main wings flaps using the rotating force of the rotating shaft of the drive motor. The ornithopter flies using aerodynamic lift generated by the flapping of the main wings.
FIG. 1 is a perspective view showing a conventional ornithopter. As shown in FIG. 1, the conventional ornithopter, which was proposed in Korean Patent Laid-open Publication No. 2003-0044625, and is entitled ‘POWER-DRIVEN ORNITHOPTER PILOTED BY REMOTE CONTROLLER’, includes a fuselage, main wings, horizontal tail wings, a battery, an electric motor, a servo motor and a main power transmission unit.
Furthermore, the conventional ornithopter, entitled ‘POWER-DRIVEN ORNITHOPTER PILOTED BY REMOTE CONTROLLER’, further includes a servo power transmission unit, which controls the horizontal tail wings depending on the rotation of the servo motor, and a controller, which controls the direction in which the servo motor is rotated and the rpm of the servo motor.
The conventional ornithopter, entitled ‘POWER-DRIVEN ORNITHOPTER PILOTED BY REMOTE CONTROLLER’ further includes a second servo motor and a vertical tail wing, which control the flight direction, as well as including the horizontal tail wings and the servo motor for controlling the horizontal tail wings.
As such, the conventional ornithopter includes a pair of main wings, and uses the principle in which it flies using the flapping of the main wings.
However, in the case of the ornithopter having one pair of main wings, it is difficult to generate sufficient aerodynamic lift and thrust to lift the weight of the ornithopter.
Even if sufficient aerodynamic lift and thrust are generated by the one pair of main wings, because the moment applied to the fuselage markedly varies depending on the position of the wings while flapping, there is a problem in that the air flow generated around the ornithopter by the flapping of the main wings is unsteady.
Therefore, forward flight in an upright position cannot be realized, because the balance of the ornithopter, which is an important factor for the forward flight in an upright position, is not maintained.
Another example of conventional ornithopters was proposed in Korean Patent Registration No. 10-0515031, entitled ‘PROPULSION SYSTEM MIMICKING HOVERING FLAPPING WING’.
This technique, entitled ‘PROPULSION SYSTEM MIMICKING HOVERING FLAPPING WING’, implements the flapping of a hummingbird, which is the only bird capable of hovering.
However, the technique, entitled ‘PROPULSION SYSTEM MIMICKING HOVERING FLAPPING WING’, pertains to hovering rather than to forward flight in an upright position. Furthermore, because the construction of the technique and a method of implementing it are complex, it is very difficult to realize the technique.
Another example of conventional ornithopters was proposed in Korean Patent Laid-open Publication No. 2006-0110241, entitled ‘DRAGONFLY-TYPE ORNITHOPTER WITH TWO PAIRS OF WING’. In this technique, two pairs of wings are disposed at front and rear positions to realize a dragonfly type ornithopter.
In the technique, entitled ‘DRAGONFLY-TYPE ORNITHOPTER WITH TWO PAIRS OF WING’, aerodynamic lift and thrust can be controlled by adjusting the difference in phase between the front and rear wings, so that the ornithopter can conduct a very difficult flight as well as hovering.
However, the technique, entitled ‘DRAGONFLY-TYPE ORNITHOPTER WITH TWO PAIRS OF WING’, is also an invention that pertains to hovering rather than to forward flight in an upright position. In other words, the object of this technique is different from that of the present invention for forward flight in an upright position.
Furthermore, in the technique, entitled ‘DRAGONFLY-TYPE ORNITHOPTER WITH TWO PAIRS OF WING’, even though the front wings and the rear wings have an exactly opposite phase difference there between, because the front wings are provided on the front part of the fuselage and the rear wings are provided on the rear part of the fuselage, vibration applied to the front part of the fuselage and vibration applied to the rear part of the fuselage have opposite phases, based on the space between the front wings and the rear wings. Therefore, it is impossible to conduct stable forward flight in the upright position.
Meanwhile, as conventional methods of remote-controlling the ornithopters using remote controllers, there are a method of remote-controlling an ornithopter by moving control sticks or circular rotating switches, which are provided on the remote controller, in desired directions, or a method in which switches are provided at left and right positions on a remote controller so that the orientation of an ornithopter varies depending on whether the left and right switches are pushed.
However, because these remote-control methods are well-known methods that have been used for a long time, there is a disadvantage in that the sense of realism in performing remote control is reduced and a user may become easily bored, soon losing interest.
In an effort to overcome the problems experienced with the conventional remote-control methods, a technique in which an object is remote-controlled by tilting or rotating a remote controller having a sensor was proposed in Korean Patent Laid-open Publication No. 2004-0056891, entitled ‘LOCATION DETECTION SENSOR USING PHOTOINTERRUP AND ITS APPLICATION TO CONTROLLER’.
However, there are disadvantages in that the method of installing the sensor in the controller and the mechanism thereof are very complex, and the cost of materials increases due to the use of the sensor.